High-performance, distributed instant messaging server written in pure C (C99-C23).

A complete rewrite of OpenIM Server (Go, 12 microservices, 100+ API endpoints) with memory pools, thread pools, ucontext coroutines, and cross-platform I/O.

┌─────────────────────────────────────────────────────┐
│                  Application Layer                    │
│  API Gateway | WS Gateway | MsgTransfer | Push | ... │
├─────────────────────────────────────────────────────┤
│                   Service Layer                       │
│  Auth | User | Friend | Group | Conv | Msg | Third   │
├─────────────────────────────────────────────────────┤
│                  Protocol Layer                       │
│  HTTP Parser | WebSocket | Binary RPC | Protobuf     │
├─────────────────────────────────────────────────────┤
│                  Data Access Layer                    │
│  MongoDB | Redis | Kafka | LocalCache | Discovery    │
├─────────────────────────────────────────────────────┤
│               Concurrency Runtime                     │
│  Coroutine Scheduler | Thread Pool | IO Multiplexer  │
├─────────────────────────────────────────────────────┤
│                 Foundation Layer                      │
│  Memory Pool | Logger | Config | Stats | Error       │
│  String Buffer | Hash Map | List | Atomic | Spinlock │
└─────────────────────────────────────────────────────┘

# Prerequisites (optional, auto-detected):
#   libmongoc, hiredis, librdkafka, libyaml, zlib, libcurl, openssl

# Debug build with tests
make build

# Run tests
make test

# Run all-in-one dev server
make dev

# Release build
make release

# Docker build
make docker

# Clean
make distclean

cmake -B build -DCMAKE_BUILD_TYPE=Debug \
  -DMIKU_ENABLE_TESTS=ON \
  -DMIKU_ENABLE_MONGO=OFF \
  -DMIKU_ENABLE_REDIS=OFF \
  -DMIKU_ENABLE_KAFKA=OFF \
  -DMIKU_ENABLE_S3=OFF
cmake --build build -j$(nproc)

# All-in-one dev server
./build/bin/miku-dev -c config/

# Individual services
./build/bin/miku-api -c config/ -p 10002
./build/bin/miku-msggateway -c config/ -p 10001
./build/bin/miku-rpc-auth -c config/

Send SIGTERM or Ctrl+C for graceful shutdown. Send SIGHUP to trigger config reload.

YAML config files in config/:

CLI flags override config: -c <dir> config dir, -p <port> API/WS port, -w <port> WS port.

• 63 modules across 6 layers
• 13 binaries (12 microservices + dev server)
• 203 API routes (Auth 5, User 32, Friend 26, Group 35, Msg 30, Conv 21, Third 15, Object 8, Batch 2, Statistics 4, JSSDK 2, Prometheus 11, Config 6, Restart 1, Admin 4, Version 1)
• 123 tests + 5 benchmarks, all passing
• Benchmarks: JSON 1.36M/s, HashMap 7.09M/s, Cache 3.97M/s, Queue 38.4M/s

• HTTP/1.1 server with keep-alive, TLS (OpenSSL), idle timeout, body size limit
• Middleware pipeline: CORS, request ID, access logging, auth, stats
• WebSocket gateway (RFC 6455) with 12 protocol opcodes, IM message parsing, user status subscriptions
• Custom binary RPC with Protobuf codec
• MsgTransfer pipeline with batch flush (Redis/Mongo/Push callbacks)
• Offline push notifications (FCM/Getui/JPUSH/Dummy providers)
• Cron task scheduler with task implementations (deleteMsg, clearS3)
• Webhook/callback system (11 event types)
• Rate limiting (sliding window)
• Per-conversation sequence number management + user read tracking
• Incremental sync (friends/blacks/groups/members/conversations)
• gzip compression/decompression
• Prometheus metrics at /admin/metrics
• Log rotation (size-based)
• Graceful shutdown (SIGTERM/SIGINT) + config reload (SIGHUP)
• Conditional compilation for all external dependencies
• Docker, docker-compose, Kubernetes manifests, systemd units

• ARCHITECTURE.md - Full architecture design document (13 sections)
• docs/openapi.yaml - OpenAPI 3.0 spec (203 routes)
• config/miku-example.yml - Config example with all options
• notes.html - Development progress log

# Docker
make docker
docker run --rm -p 10002:10002 miku:latest

# Docker Compose (all 12 services)
make docker-compose-up

# Kubernetes
kubectl apply -f deploy/k8s/

# Systemd
sudo bash deploy/systemd/install.sh

• Language: C99-C23 (no C++)
• Memory: Arena + Slab pools, per-request allocation
• Concurrency: ucontext stackful coroutines, work-stealing thread pool
• I/O: epoll (Linux), kqueue (macOS planned), IOCP (Windows planned)
• RPC: Custom binary protocol with Protobuf codec
• External: mongoc, hiredis, librdkafka, libyaml, zlib, libcurl (all optional/conditional)
• Build: CMake 3.16+